Dust cover for automatic telephone switches



Nov. 10, 1953 D. PEARSALL DUST COVER FOR AUTOMATIC TELEPHONE SWITCHES Filed June 12, 1950 I INVENTOR O Luther D-Fear5a1l,

ATTORNEY Patented Nov. 10, 1953 DUST COVER FOR AUTOMATIC TELEPHONE SWITCHES Luther D. Pearsall, Fayetteville, N. 0.

Application June 12, 1950, Serial No. 167,643

1 Claim.

In automatic telephone switches (known as Strowger switches) used with the link circuits in telephone exchanges, the contacts are subject to deterioration at a more rapid rate than that due to use alone. This because the accumulation of dust on the bank contacts shortens the life of the latter and the wipers by preventing good electrical connections. Additionally the faulty connections resulting from dust cause irritating noises and interruptions in the transmission of musical notes, a serious defect when radio programs are carried through on these contacts, as is frequently the case.

Because of the very great number of contacts involved in one switch and the number of switches included in an exchange, the operation of keeping the contacts clean (they are built in banks) is a tedious one, being practically continuous, since, when the last have been cleaned, in the average exchange, the first are again in condition to require attention, if performance is to be kept up to standard.

The object of the present invention, therefore, is to provide a cover by which the switch contacts will be enclosed, so that dust accumulations thereon will be reduced to a minimum; to provide a dust cover with busy key and test-jack openings with which are incorporated dust-excluding features; and generally to provide a device of the kind indicated which is made of transparent material and which is simple in construction and is, therefore, susceptible of cheap manufacture and sale.

With this object in view the invention consists in a construction and combination of parts of which a preferred embodiment is illustrated in the accompanying drawings in which Figure 1 is an elevational view of the so-called Strowger switch, showing the manner in which the cover is used;

Figure 2 is a perspective of the cover detached;

Figure 3 is a top plan View;

Figure 4 is a left-hand side elevational view;

Figure 5 is a front elevational view;

Figure 6 is an elevational view, looking, at the right-hand side of the cover for the terminal switch of a row.

While the invention may be fabricated from sheet material cut and assembled to form an enclosing casing for the banks 10 of contacts of the switch S, it is preferably an integral structure with the side wall II, the front wall [2 and the top and bottom walls I3 and M, the bottom wall merging into the front walls on a moderate curve, as indicated at l5. Except the cover for the terminal switch of a row, which is provided with a side wall I la, all the covers omit this latter wall, that is, they are open on one side but, when in use, have this open side closed with the wall ll of the adjacent switch cover.

In use the cover is supported from the switch base 16, the top [3, being cut away, as indicated at ll, to correspond to the perimetrical contour of the switch base from which depend the banks [0 of contacts suspended on the bank rods [8 along with the top plate 19 which is directly under the base and on which the top wall l2 rests.

Within, the cover, from which the back is omitted, carries the rubber suction cups 20 which are positioned directly below the bank rods and engage the latter on the lower ends, the cups steadying the position of the cover when mounted.

While transparency is not an essential, it is a valuable attribute in a device of this kind, and, therefore, the cover had best be made of transparent material, preferably plastic.

To avoid the necessity for its removal for testing and busying out, the cover is formed with access openings 2| and 22, the former being for the busy key and the latter for the test-jack. Each of the openings is provided with a dust wing, the one, indicated at 23 extending inwardly from the lower edge of the busy key opening, and the other, indicated at 24, extending inwardly from the left-hand lateral edge of the test-jack opening.

With the use of a cover, which is obviously readily removable and replaceable, dust accumulations with their deleterious effects are reduced to a minimum, yet the testing and busying out functions are susceptible of being performed with it in place.

The invention having been described, what is claimed as new and useful is:

A dust cover for enclosing the contacts and wipers of an automatic switch in telephone exchanges comprising a manually detachable frictionally retained casing including sides, front, top and bottom, the back of the casing being open to permit the casing to be slidably engaged over the contacts and wipers, the top of the casing being provided with an opening for engagement with a fixed part ofthe switch, resilient cups on the bottom of the casing for engagement with parts of the switch, the front and one side wall of the casing being provided with busy key and test-jack openings, respectively, a dust Wing extending from one edge of each opening to minimize possibility of dust accumulating on the contacts and wipers.

LUTHER D. PEARSALL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,204,606 Stearns Nov. 14, 1916 1,322,995 Barnum Nov. 25, 1919 2,040,334 Reynolds May 12, 1936 

